Library for Jinja2 Template Extensions

Provides a library functionality for Jinja2 extensions that can be used in templates.

FEATURES:

• Provides a library concept for Jinja2 extensions, like filters, tests, globals and directives (aka: extensions),
• Declarative approach to describe and register Jinja2 extensions.
• Simplifies how library items are registered in an Environment (in one step).
• Supports own namespace/scope for each library.
• Supports control over registered names.

EXAMPLE 1: Basic Example

# -- FILE: example/hello.py
from jinja2_library import Library
import jinja2.ext

this_library = Library()
register = this_library.make_register_decorator()

@register.filter
def hello(value, greeting=None):
    greeting = greeting or "Hello"
    return u"{greeting} {name}".format(greeting=greeting, name=value)

class LibraryExtension(jinja2.ext.Extension):
    """Simplifies to use ``this_library`` as Jinja2 extension."""
    def __init__(self, environment):
        super(LibraryExtension, self).__init__(environment)
        this_library.add_to_environment(environment)

The template library can be used by using the LibraryExtension class in Jinja2:

# -- FILE: use_template_library_hello.py
# USING: example.hello.LibraryExtension
from jinja2 import Environment
from assertpy import assert_that

this_extension = "example.hello.LibraryExtension"
this_template = "HELLO: {{ this.name|hello(greeting=this.greeting) }}"
this_data = dict(name="Alice", greeting="Ciao")

environment = Environment(extensions=[this_extension])
template = environment.from_string(this_template)
this_text = template.render(this=this_data)
assert_that(this_text).is_equal_to("HELLO: Ciao Alice")

API

Library class

The Library constructor provides the following parameter:

• The scope parameter allows to provide a namespace for the registered Library items.
• This prevents name collisions if many filters/tests/globals are used.
• Simplifies the registration of filters/tests/globals/extensions into an Environment.

EXAMPLE:

# -- FILE: example/scoped_hello.py
from jinja2_library import Library
import jinja2.ext

this_library = Library("foo.bar")  # -- HINT: Library with scope="foo.bar".
register = this_library.make_register_decorator()

@register.filter(name="hello")
def hello_filter(value, greeting=None):
    greeting = greeting or "Hello"
    return u"{greeting} {name}".format(greeting=greeting, name=value)

class LibraryExtension(jinja2.ext.Extension):
    def __init__(self, environment):
        super(LibraryExtension, self).__init__(environment)
        this_library.add_to_environment(environment)

Scoped library names can then be used inside a template, like:

{#- FILE: template.jinja -#}
{#- USING: extensions=["example.scoped_hello.LibraryExtension"] -#}
HELLO: {{ this.name|foo.bar.hello(greeting="Ciao") }}

Register Decorators

This Python package provides the following decorators (in the context of the example above):

The function decorators for @register.filter/test/global_ support optional parameters. These optional decorator parameters are:

Background Info

Inspired by the Django template library approach.

History

• INITIALLY CREATED AS: simplegen.template_lib
• REFACTORING: Extracted into own standalone package to simplify reuse with Jinja2 template engine.